Here's what saved my bacon last year, and may again this year. I bought hay by the truckload in the spring, before everyone knew we were going to have a drought. Woulda been a bad move if Farmer's Almanac was wrong, but it wasn't. This year I have had my hay in since May. I didn't worry too much about the quality as I'm only going to use it as a pacifier and filler. They will get their nutrition from Purina's Omolene 400. That's a complete feed, but I like to let them have a decent amount of hay, not all they'd like but say, 5-8 lbs per feeding instead of free choice. I feed the amount of Omolene 400 per the bag instructions and I would bring the horses in to the barn and blanket to keep them dry and warm. Our winter was uncharacteristically warm last year, this year Farmer's Almanac says cold early and colder than normal. I'm washing blankets and getting them ready now.
I'm also buying an extra 1/2 pallet of Omolene when I buy my feed and stocking it up. I don't board so having someone walk off with my feed isn't really a worry, but I do keep my feed barn locked, just in case.
With 2 horses, guessing they should each weigh 1000 lbs (just to make the example easy), you'll be feeding roughly half a bag per day (25 lbs), if you let the barn owner just feed the hay. So, a pallet = 40 bags, it should last you roughly 80 days per pallet. I'm not sure when you start to get cold or how long it lasts, but for 2 horses, you might be able to get by with 2 pallets until next spring? If not, then 3 for sure and you'd have more than enough to help another boarder who doesn't get stocked up as well.